What is the IEC 60118-4 standard for hearing loops?

IEC 60118-4 specifies a target magnetic field strength of 400 mA/m (±3dB) at the listener ear height, typically 1.2m seated. This ensures hearing aid users with telecoil (T-coil) can receive a clear, consistent audio signal throughout the looped area. The standard also covers frequency response (100Hz to 5kHz) and signal-to-noise ratio requirements.

When should I use a phased array instead of a perimeter loop?

A phased array system is recommended for rooms wider than approximately 8 metres, rooms with significant metal in the floor or structure (such as raised access floors or steel frames), and spaces requiring very even field strength distribution. Phased arrays use two interleaved sets of parallel cables driven with a phase shift, which cancels out overspill and provides more uniform coverage than a simple perimeter loop.

Are hearing loops a legal requirement in the UK?

Under the Equality Act 2010, service providers must make reasonable adjustments for people with disabilities, including those with hearing loss. Approved Document M of the Building Regulations requires hearing enhancement systems in reception areas, ticket offices, meeting rooms, and performance spaces. BS 8300:2018 also recommends hearing loops in publicly accessible buildings.

How does floor construction affect hearing loop performance?

Metal in floor construction absorbs the magnetic field generated by the loop cable, reducing the signal reaching hearing aids. Concrete slabs have minimal metal loss. Timber floors with noggins may have 10-20% loss. Raised access floors with steel pedestals and panels can cause 30-50% or more signal loss, often requiring phased array systems and higher amplifier power to compensate.

What cable size should I use for a hearing loop?

The most common cable for hearing loops is 2.5mm² flat copper conductor. For larger installations or long cable runs, 4mm² cable reduces resistance and allows lower amplifier power. The cable should be installed flat against the floor or in the wall, routed to avoid crossing over itself, and kept away from mains cables to prevent interference.

Hearing Loop Calculator — Cable Length & Amplifier Sizing

How We Calculate This

This calculator determines the cable length, amplifier power, and system type needed for a hearing loop installation compliant with IEC 60118-4 and UK Building Regulations.

Field strength target

IEC 60118-4 requires a magnetic field strength of 400 mA/m (±3dB) at the listener's ear height. The calculator determines the current needed in the loop cable to achieve this, accounting for room dimensions and metal loss factors.

System selection

For rooms up to approximately 8m wide with low metal loss, a simple perimeter loop (cable around the room edges) provides adequate coverage. Larger rooms, high metal-loss environments, or spaces needing uniform coverage use a phased array with two interleaved cable arrays driven out of phase.

Amplifier sizing

Amplifier power is calculated from the required drive current and total cable impedance, with adjustments for background noise levels. The formula is:

Power = I² × R × noise factor × safety margin

I: Current required to achieve 400 mA/m field strength
R: Total cable loop resistance (ohms)
Noise factor: Compensation for ambient noise above 50dB

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.

Hearing Loop Calculator - IEC 60118-4 Cable Length & Amplifier Sizing